Sewer Pipe Inspections

Closed Circuit Television (CCTV) is used to inspect the 218 miles of existing sanitary sewer pipe for defects such as: root intrusion, fractures, infiltration, exfiltration, separated pipe, and collapsed pipe. Wastewater pipelines in the City are comprised of a variety of materials that age at different rates and the necessitate inspection at regular intervals to assess their condition.

The Wastewater Division currently CCTV inspects the entire City on a 4-year cycle. Inspections are performed more frequently in areas known to be prone to problems such as commercial areas or areas that were constructed prior to the adoption of stringent construction standards. Inspection data are used to plan capital improvement projects (determine if a pipe needs replaced or relined). CCTV inspection can also determine why a sanitary sewer overflow happened as well as locate and document service connections.

The CCTV crew inspects all newly constructed pipes for joint integrity, proper slope (to allow for drainage), and for damage to line segments during construction. Using the information gathered during these inspections, the City of Redmond can mandate contractors correct defects prior to the City assuming ownership of the pipelines. After the pipeline has been in service for one year, the CCTV crew inspects the pipeline again to determine if defects have developed. If defects are noted, contractors are required to complete repair of the damaged pipe segment prior to the release of maintenance bond monies.

CCTV is cutting edge technology that utilizes a television camera mounted on a robotic device that is connected to a 1200-foot cable. The robotic system is placed directly into the sewer through a manhole.

Technician lowering robotic camera system into a manhole in City street.

Once inside the sewer pipe, the robotic device is operated by remote control located inside a City vehicle. The CCTV system relays live footage from within the sewer to a high-resolution monitor in the CCTV truck.

If a defect is discovered, the operator can investigate the defect in detail. The camera’s capabilities allow the operator to look in all directions. An electronic footage counter is connected to the camera, enabling the operator to note the exact location of defects, service connections, and blockages. A report of each sanitary sewer pipe segment is digitally stored and is utilized if a section of pipe is in need of repair. The video is also stored on a City server.

Here’s what the closed circuit television (CCTV) inspection set-up looks like in a City street. The vehicle parked in front is the CCTV truck. The vehicle parked in back is the vacuum truck. You can see the vacuum truck’s hose has been inserted into the same manhole as the robotic camera system.

This video shows what fat, oil, and grease (FOG) build-up looks like inside a wastewater pipe. The video ends once the robotic camera system reaches a manhole. A hose from the City’s vacuum truck can be seen in the manhole sucking-up the incoming wastewater. This is done to make sure wastewater flow doesn’t block the camera’s view while it’s traveling down the pipe toward the manhole.